1. Field of the Invention
The present invention relates in general to belt tensioners and more particularly to a belt tensioner for use in a belt drive unit for driving a water pump and a cooling fan, for instance, of an automobile engine.
2. Description of the Prior Art
In most belt tensioners and particularly of the type wherein a cog belt is used, it is necessary to fit one or more belt tensioners since if the tension of the belt is lower than a predetermined amount, an efficient power transmission cannot be attained.
FIGS. 1 and 2 show a typical belt tensioner 10 for a belt drive unit of an automobile engine. The belt tensioner 10 comprises a bracket 12 which is fixed to a stationary member 14 by means of bolts 16 and 18. When, however, the bolts 16 and 18 are loosened, the bracket 12 can be rotated about the bolt 16. The bracket 12 has rotatably mounted thereon a pully 20 and is urged by a spring 22 to rotate in the clockwise direction in the drawing, that is, in the direction to cause the pully to move toward a belt 24.
With the belt tensioner 10 of the above described type, an easy belt tension adjusting operation results since the pully 20 becomes urged toward the belt 24 by the effect of the spring 22 when the bolts 16 and 18 are loosened.
This type of belt tensioner 10, however, is disadvantageous since it is relatively bulky and requires a relatively large space for its arrangement adjacent the engine. Hence, there has been a difficulty in effectively fitting the belt drive unit with such type of belt tensioner. This is particularly true in the case of application of the belt drive unit having such belt tensioner to an engine of a F-F type automotive vehicle in which the engine is mounted at the front of the vehicle to provide a front wheel drive and whose engine compartment is particularly congested.